The objective of this project is to develop a system consisting of instrumentation, reagents and methods for rapid cell-based assays of ligand binding to G protein-coupled receptors and for rapid assessment of cellular response. The approach is based on measuring fluorescence resonance energy transfer (FRET) between fluorescent ligand conjugates (acceptor) and G protein-coupled receptor intrinsically tagged with green fluorescent protein (donor). A key innovation of the approach is the use of a new fluorescence lifetime sensing technology, recently developed by Ciencia, for measuring ligand binding. That is, the binding of ligand is transduced as a decrease in the fluorescence lifetime of the green fluorescent protein. The long term objective is to develop compact, robust, sensitive, low-cost instrumentation for high throughput screening in drug discovery. The proposed work addresses the needs of pharmaceutical companies which are under competitive pressures to bring successful new therapeutic products to market faster and more efficiently. The enormous libraries of lead chemical compounds assembled from natural sources such as plants, ocean life, and fungi or from combinatorial techniques have created a need for better, faster and cheaper technologies for high throughput screening. One of the most important classes of drug targets for pharmacological intervention is the family of G-protein coupled receptors (GPCR). The market potential for drugs targeted to GPCR is huge. Already, they comprise about 60% of all drugs manufactured today, and account for one of the largest target families resulting from the Human Genome Project. To our knowledge, this would be the first time for fluorescence lifetime sensing is exploited for high throughput screening applications. PROPOSED COMMERCIAL APPLICATION: High throughput screening in lead drug discovery, cell and molecular biology research instrumentation, clinical diagnostic instrumentation.